1. Field of the Invention
This invention relates to a housing construction for a portable type radio telephone device.
2. Description of the Prior Art
FIG. 1 is an external perspective view showing a conventional housing construction for a portable type radio telephone device. FIG. 2 is a cross-sectional view of the same, in which reference numeral 1 designates an upper cover usually made of plastic, on which a display portion 1a and an operating button portion 1b and the like are disposed.
Reference numeral 2 designates a lower cover within which a main unit of a radio telephone device is fixedly mounted. This lower cover 2 is made, for example, by aluminum die casting, has a good thermal conductivity, is adapted to be combined with the upper cover 1, and has a partitioning wall 2a integrally formed therein.
Reference numeral 3 designates a battery pack which serves as a power source for the portable radio telephone device. The battery pack 3 forms a part of the lower cover 2 and is detachably mounted on the back of the portable radio telephone device, i.e., the lower portion of the upper cover 1. Reference numeral 4a designates an internal unit for controlling various functions required for enabling operation of a portable radio telephone device. Internal unit 4b has a synthesizer portion and a receiver portion which form essential components enabling operation of the portable radio telephone device. Internal unit 4c transmitter output portion which generates the largest amount of heat in the portable radio telephone device. Also, external connector 5 is for supplying power from an external power source to the device and can be connected to other optional instruments.
Reference numeral 8 designates a radiant contact surface for conducting the heat of the internal unit to the lower cover 2, and 11 designates a rebound leaf for urging the internal unit 4c against the lower cover 2 to obtain a close contact with the radiant contact surface 8.
The operation of the device will be described hereinafter. When the portable radio telephone device is being used, the internal units 4a and 4c generate heat to some extent, and the heat is radiated from the outer surface of the portable radio telephone device by conduction, convection and radiation.
In the case where the portable radio telephone device is used in the transmitting state, the internal unit 4c as a transmitter output portion generates a relatively large quantity of heat. Because of this, the heat generating portion of the internal unit 4c is mounted in such way that it is directly in close contact with the inner surface of the lower cover 2. This contact is secured by the rebound leaf 11, and the heat from the internal unit 4c is effectively conducted to the lower cover 2 which has a large heat capacity, so that the device is maintained within an acceptable temperature rise.
Since the conventional portable radio telephone device is constructed as described above, the heat from the internal unit 4c, having a large heat generating quantity, is efficiently conducted to the lower cover 2 made of a metal having a good thermal conductivity which forms the outer surface of the portable radio telephone device. Consequently, the temperature of the outer surface of the portable radio telephone device becomes increasingly higher as it is being used.
Therefore, in the case that the portable radio telephone device is used for a long period of time, the temperature of the outer surface of the portable radio telephone device sometimes becomes too high to be comfortably held by hand. As a protective measure, a circuit for restricting the use of the portable telephone radio device is required to prevent the device from being used for a period in excess of a given time. This causes a problem in that the device cannot be continuously used.
Furthermore, another problem arises in that when the portable radio telephone device is first held by hand from its holding state when a temperature is extremely low, in a winter season or the like, the device is too cold to be comfortably held by hand.
Alternatively, the outer surface of a portable radio telephone device may be formed from a resin-made cover having a thermal insulating effect in order to keep the external temperature low enough to be comfortably held by hand. This also poses a problem in that the temperature rise within the portable radio telephone device increases because of the heat insulating effect, and the reliability of the portable radio telephone potentially could be impaired.